Second generation (2G) mobile communication refers to transmission and reception of voice into digital and is represented by Code Division Multiple Access (CDMA), Global System for Mobile communication (GSM) and the like. General Packet Radio Service (GPRS) was evolved from the GSM. The GPRS is a technology for providing a packet switched data service based on the GSP system.
Third Generation (3G) mobile communication refers to transmission and reception of image and data as well as voice (audio). Third Generation Partnership Project (3GPP) has developed a mobile communication system (i.e., International Mobile Telecommunications (IMT-2000)), and adapted Wideband-CDMA (WCDMA) as Radio Access Technology (RAT). The IMT-200 and, the RAT, for example, the WCDMA are called as Universal Mobile Telecommunication System (UMTS) in Europe. Here, UTRAN is an abbreviation of UMTS Terrestrial Radio Access Network.
Meanwhile, the third generation mobile communication is evolving to the fourth generation (4G) mobile communication.
As the 4G mobile communication technologies, a Long-Term Evolution Network (LTE) whose standardization is being carried on in 3GPP and IEEE 802.16 whose standardization is being carried on in IEEE have been introduced. The LTE uses a term ‘Evolved-UTRAN (E-UTRAN).’
The 4G mobile communication technology has employed Orthogonal Frequency Division Multiplexing (OFDM)/Orthogonal Frequency Division Multiple Access (OFDMA). The OFDM uses a plurality of orthogonal subcarriers. The OFDM uses an orthogonal property between Inverse Fast Fourier Transform (IFFT) and Fast Fourier Transform (FFT). A transmitter performs the IFFT for data and transmits the data. A receiver performs the FFT for a received signal to recover original data. The transmitter uses the IFFT for concatenating a plurality of subcarriers, and the receiver uses the corresponding FFT to segment the plurality of subcarriers.
Meanwhile, the 3G or 4G mobile communication system has a function part for calculating the position (or location) of a terminal to provide a location service that provides the location of the terminal.
Currently, there are several methods for calculating the location of the terminal, including a cell-ID method for transferring an ID of a cell to which a mobile terminal belongs, a method for calculating the location of a terminal through triangulation by measuring time taken for radio signals to reach each base station from the terminal, and a method of using a satellite.
In the cell ID based (i.e. cell coverage) method, a position of an UE is estimated with the knowledge of its serving base station (i.e., a serving Node B). The information about the serving Node B and cell may be obtained during a paging procedure, a locating area update procedure, a cell update procedure, an URA update procedure, or a routing area update procedure
The cell coverage based positioning information can be indicated as the Cell Identity of the used cell, the Service Area Identity or as the geographical co-ordinates of a position related to the serving cell. The position information includes a QoS estimate (e.g. regarding achieved accuracy) and, if available, the positioning method (or the list of the methods) used to obtain the position estimate.
When geographical co-ordinates are used as the position information, the estimated position of the UE can be a fixed geographical position within the serving cell (e.g. position of the serving Node B), the geographical centre of the serving cell coverage area, or some other fixed position within the cell coverage area. The geographical position can also be obtained by combining information on the cell specific fixed geographical position with some other available information, such as the signal RTT in FDD or Rx Timing deviation measurement and knowledge of the UE timing advance, in TDD.
Meanwhile, for the method of using the satellite, UE has to be equipped with radio receivers capable of receiving GNSS signals. Indeed, examples of GNSS include a GPS (Global Positioning System) and Galileo. In this concept, different GNSS (e.g. GPS, Galileo) can be used separately or in combination to perform the location of a UE.
Also, the method using a triangulation technique may be divided into two type techniques. The one is a U-TDOA positioning method and the another is an OTDOA-IPDL (observed time difference of arrival with network adjustable idle periods in down link) method.
First, The U-TDOA positioning method is based on network measurements of the Time Of Arrival (TOA) of a known signal sent from the UE and received at four or more LMUs. The method requires LMUs in the geographic vicinity of the UE to be positioned to accurately measure the TOA of the bursts. Since the geographical coordinates of the measurement units are known, the UE position can be calculated via hyperbolic trilateration. This method will work with existing UE without any modification. In most cases the UEs deeply inside the cell coverage radius does not need to receive signals from other cells. Only when the UE moves to cell coverage edge, it needs to listen to signals from other cells and possibly handover to other cells. This is contrary to the UE location acquisition procedure, where the UE may need to listen to more than 1 cell regardless of UE geographical position.
Second, The OTDOA-IPDL (observed time difference of arrival with network adjustable idle periods in down link) method involves measurements made by the UE of the frame timing (e.g. system frame number ? to system frame number observed time difference)
FIG. 1
FIG. 1 illustrates an exemplary OTDOA method.
Referring FIG. 1, the OTDOA-IPDL (observed time difference of arrival with network adjustable idle periods in down link) method involves measurements made by the UE of the frame timing (e.g. system frame number ? to system frame number observed time difference). These measures are used in the network and the position of the UE is calculated. The simplest case of OTDOA-IPDL is without idle periods. In this case the method can be referred to as simply OTDOA. The Node B may provide idle periods in the downlink, in order to potentially improve the hearability of neighboring Node Bs. The support of these idle periods in the UE is optional.
As such, in the OTDOA technique, the UE has to measure the timing difference. But, if bandwidths allocated by each cell are different each other, the UE suffers from measuring the timing difference.